Washington: India's largest maker of generic drugs, Ranbaxy Laboratories Ltd has won US approval to sell a generic version of the world's top-selling cholesterol lowering drug Lipitor hours after it lost US patent protection.

The US Food and Drug Administration (FDA) late Wednesday said it granted Ranbaxy approval to sell a generic version of Pfizer Inc.'s Lipitor, called atorvastatin calcium.

The company will make generic tablets in 10 mg, 20 mg, 40 mg and 80 mg strengths. The drug will be manufactured by Ohm Laboratories in New Brunswick, New Jersey.

The last-minute decision ended widespread speculation over the outcome of a delay caused by long-standing manufacturing issues at some Ranbaxy factories.

People who have high blood cholesterol levels have a greater chance of getting heart disease, FDA said. By itself, the condition usually has no signs or symptoms. Thus, many people do not know that their cholesterol levels are too high.

"This medication is widely used by people who must manage their high cholesterol over time, so it is important to have affordable treatment options," said Janet Woodcock, director of the FDA's Centre for Drug Evaluation and Research.

"We are working very hard to get generic drugs to people as soon as the law will allow."

In the clinical trials for Lipitor, the most commonly reported adverse reactions in patients were: inflammation of the nasal passages, joint pain, diarrhoea, and urinary tract infection.

Generic drugs approved by FDA have the same high quality and strength as brand-name drugs. The generic manufacturing and packaging sites must pass the same quality standards as those of brand-name drugs, FDA said.